With the arrival of fall, many areas will see an increase in wet weather. When landing on wet runways or runways contaminated by standing water, it is inevitable that some form of hydroplaning will happen. It is important to understand the phenomenon and what to do when you encounter it.
What is Hydroplaning
Hydroplaning happens when the aircraft experiences reduced or total loss of friction between the wheels and runway surface. The effects can often mimic sliding on ice and can result in sliding or drifting off the runway. This risk is increased when the aircraft is caught in a crosswind during this loss of friction, pushing the aircraft toward the runway edge. Due to the decrease in friction, hydroplaning results in reduced directional control and longer stopping distances.
Types of Hydroplaning
There are three types of hydroplaning: dynamic hydroplaning, reverted rubber hydroplaning, and viscous hydroplaning. It is possible to experience more than one of these in a single incident, and you may not always experience them to the same degree.
In dynamic hydroplaning, the water being displaced by the aircraft produces sufficient pressure to lift the wheels partially or completely off the ground. When the wheels are no longer in contact with the runway surface, this is called total dynamic hydroplaning.
Reverted rubber hydroplaning happens when the brakes have been locked in place, often during an attempt to control another type of hydroplaning. As the wheels heat up, the rubber begins to melt and heat the water on the runway surface. This creates steam between the wheel and the runway surface, causing the tires lose friction.
While dynamic hydroplaning tends to happen at higher speeds, viscous hydroplaning happens at low speeds while using smooth runways. This tends to happen when a layer of oil or water creates an impenetrable barrier on the runway preventing the wheels from gaining friction.
How to Minimize the Effects of Hydroplaning
There has been an effort to combat the effects of hydroplaning by building grooved runways. While this has proven to be very effective, it is important to keep in mind it may not completely mitigate the effects of hydroplaning, or that you may not always have access to a grooved runway.
When conditions for hydroplaning are present during landing, ensuring that you achieve a firm touchdown is more important than making that elusive smooth-as-silk landing. Remember, your touchdown should be at the slowest speed possible, and you should use your rudder to maintain control rather than the nosewheel steering. In addition, it’s important to remember that once the nosewheel is lowered, only moderate braking is necessary. If you feel the aircraft start to hydroplane, pull the nosewheel back up and use some aerodynamic drag to slow down. If you think, the aircraft has begun reverted rubber hydroplaning, release the brakes, allowing the wheels to spin up.
By following the general guidelines for takeoff and landing on contaminated runways as well as any manufacturer guidance, it is possible to decrease the amount of hydroplaning related accidents.
- Pilot Guide to Takeoff Safety
- Wet or Contaminated Runways
- Pilot Braking Action Reports
- AC 91-79A Mitigating the Risks of a Runway Overrun Upon Landing
- Contaminated Runways Airport/Runway Data
Related CTS Training: